It sounds like you have two issues here.
First, you have a cocker, and they were bred to be retrievers. So she is retrieving all the toys.
Second, it sounds like she is resource guarding. Meaning that everything of interest is her’s. Seems to be a female dog thing. My female boxer did it from the time she was very young and never allowed her brother to play with toys. He had to wait until she died to have fun.
You can break this with training but it take time and there is no easy fix. Check with behaviorist trainers in your area. Maybe they can offer a suggestion with out a huge charge.
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